1. Evento 2005
Requested Report

2. 2005 Event : The Emergence of RLO
The Outbreak
During the period of April to July, 2005, the tilapia farms operating in Costa Rica’s Arenal-Tempisque Irrigation District experienced an epidemic disease outbreak resulting in losses of stocks.
This outbreak followed the appearance in March and April of 2004 of a peculiar nodular structure in the fillet meat of tilapia from two of the farms supplying Terrapez, and was accompanied by comparatively light mortality.
Multiple symptoms and disease agents were observed in early diagnostic efforts carried out with national laboratory resources, and in particular, several university fish disease laboratories in the USA.
Among other common warm water bacterial diseases, presumptive diagnosis of a Rickettsia Like Organsim (RLO) was made in 2004 and confirmed at the molecular level in 2005.
RLO bacteria strains have attacked farmed tilapia populations in Asia, Hawaii, the Caribbean, and the USA in recent years. They have also emerged as agents of concern in cod (Norway), hybrid striped bass (USA), salmon (Chile) and Isaki (Japan).
The Origin and Cause
The origin of the RLO in Costa Rica is unknown, but may have been the result of fish importations to the region, foreign visitors, migratory birds, disturbance of organic sediments in Lake Arenal due to low water levels and high winds, etc.
Research has shown a clear relation between extreme water temperature changes and the onset of the disease; and this was observed to be a conspicuous factor during the winter and spring of 2005.
The chain reuse of water within a farm is also a problem leading to the spread of any disease. 2 2

3. 2005 Event : The Emergence of RLO (Cont..)
Remedial Measures
Immunity
Affected tilapia stocks are expected to develop a certain degree of auto-immunity to the disease, and this has been observed at ACI as well as in other parts of the world.
Antibiotic Therapy
Initially, the lack of experienced veterinary resources within the company or in the country, and the lack of experience on the part of farm staff with the use of antibiotics (historically not required with tilapia at ACI), resulted in unsuccessful attempts to control the disease using aquaculture drugs during 2005.
Subsequently, proper application of FDA approved antibiotics has proven effective in reducing mortality associated with RLO and its secondary infectious agents. Currently, although disease is still present in the farms, key production indicators are back to normal. 3 3

4. 2005 Event : The Emergence of RLO (Cont..)
Remedial Measures
Vaccines
The development of vaccines against the local strain of RLO and collateral agents promises to be the most effective long term strategy.
Grupo-ACI is presently engaged with a prominent vaccine manufacturer with previous experience in treating the RLO syndrome. Results from early trials have proven difficult due to the need to include the collateral agents in the vaccine treatment; however the most recent trials suggest a distinct economic advantage with the use of the vaccine as opposed to reliance solely on antibiotic therapeutants.
Management
The company has hired one full time senior and one junior professional veterinerian, who administer a comprehensive health strategy and action plan on all Group farm sites.
The company has instituted a comprehensive bio-security plan and operational protocols designed to minimize the spread of disease. 4 4